Air North Brasilia Crash in Darwin (Merged)
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Ron's old school; I think he flew DC3's in the RAAF a hundred years ago, and from some of the training I saw at the Aero Club in a Partenavia,real heroic stuff over at D212, I wouldn't put a lot of store in what he says.
Part of the problem which has not been raised fully in this discussion is the type of training that training pilots get these days. I was a former Instructor and that helped me considerably during the training part of my career when there was no sim and all the flying had to be undertaken in the aircraft. Sound planning and conservative scenario's provided the basis for training in the aircraft that was a safe as possible.
Later in my career I was with a company where the training and checking pilots were selected often on the basis of being mates with the boss or CP, not their ability to impart knowledge. This reflected down the line when one found out what new F/Os were not taught! Sadly at the time CASA could not give a rats and just endorsed the company selection. With the advent of the sim, the training was still deficient because the 'old guard' experience was not often there to cover off what many believe to be the basics.
Now many of the "basics" are just not taught! We could start with airmanship and what those pedals on the floor are for!
These comments are generic and do not relate to this tragic accident, the company or crew involved.
Later in my career I was with a company where the training and checking pilots were selected often on the basis of being mates with the boss or CP, not their ability to impart knowledge. This reflected down the line when one found out what new F/Os were not taught! Sadly at the time CASA could not give a rats and just endorsed the company selection. With the advent of the sim, the training was still deficient because the 'old guard' experience was not often there to cover off what many believe to be the basics
Last edited by RENURPP; 28th Mar 2010 at 02:35.
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In this category all V1,Vr and V2 are taken from RTOW charts in the A/C generally in a book next to the seat or the ships library, it is possible to get it wrong however at these weights a couple of knots here or there will only make a difference if you are a test pilot. The A/C will accererate that quickly and I tend to think even 1 inop ( unless auto feather failure hasnt occured and yes there are other things that can go wrong ) the machine powers away very well. Actuals are rarely used as assumed temps are generally the go.
Grandpa Aerotart
Thirdly, deceleration starts as soon as you close the thrust levers
At the instant that thrust is removed the rate of acceleration starts to decrease but actual deceleration starts some period of time later.
If an aircraft is being accelerated at say 10m/sec/sec it doesn't instantly go to -1m/sec/sec but rather experiences an acceleration rate of 9/8/7/6/5/4/3/2/1 m/sec/sec first.
It may FEEL like deceleration but its actually reducing acceleration.
remoak
I’m not sure what aircraft you fly and/or whether it has a full EFIS setup but the last time I was in the sim the Speed Trend arrow on the speed tape of my PFD didn’t go from acceleration to deceleration in an instant. It did exactly as Chimbu Chuckles has stated. The acceleration decreases over time once the power is reduced or removed before the aircraft started to decelerate.
I’m not sure what aircraft you fly and/or whether it has a full EFIS setup but the last time I was in the sim the Speed Trend arrow on the speed tape of my PFD didn’t go from acceleration to deceleration in an instant. It did exactly as Chimbu Chuckles has stated. The acceleration decreases over time once the power is reduced or removed before the aircraft started to decelerate.
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f.nose
Most operators have TOLD (TO and landing data cards) cards kept within reach in the cockpit. Usually speeds determined in increments of 250kg or 500lbs, so some small rounding errors are possible but would only make a difference of a knot or so....no biggy!
Does anyone know the actual method for calculating V1 on the Braz? and Is it possible to get it wrong?
Not suggesting that was the problem here, just curious
Not suggesting that was the problem here, just curious
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remoak
To be fair, comparing an engine failure in a four engine jet with a two engine turbo prop is not comparing apples with apples.
Again, using the 146 as an example, if you take off using flex thrust (as you normally would at training weights), there is no requirement to increase thrust to N1ref if you suffer an engine failure. You can if you want, but you don't have to as the flex thrust performance allows for the engine failure case. So for the 146, you have even less of an issue with controllability as the assymetric thrust is lower than it would be with full thrust.
Chimbu, if there is no thrust there is no acceleration. There is no requirement for acceleration to reduce gradually. Movement is subject to inertia and momentum but acceleration is not. Any perceived delay in deceleration would be due to delays in the engine responding to power lever inputs.
404Titan, with your speed trend you are seeing delays in engine response, the engine will not go from T/O thrust to idle instantly. The statement that acceleration stops the instant the thrust levers are closed is wrong because the engine can't respond that quickly, but if you think that you can remove all thrust and still experience positive acceleration then you are also wrong.
404Titan, with your speed trend you are seeing delays in engine response, the engine will not go from T/O thrust to idle instantly. The statement that acceleration stops the instant the thrust levers are closed is wrong because the engine can't respond that quickly, but if you think that you can remove all thrust and still experience positive acceleration then you are also wrong.
[QUOTE]Chimbu, if there is no thrust there is no acceleration. There is no requirement for acceleration to reduce gradually. Movement is subject to inertia and momentum but acceleration is not. Any perceived delay in deceleration would be due to delays in the engine responding to power lever inputs/QUOTE]
I beg to differ.
It depends on the mass of the object and rate of acceleration.
Think of a bullet being fired from a gun. The bullet is initially at rest until a charge is applied and it then accelerates until equilibrium is achieved before starting to decelerate. Thrust is removed the moment the bullet leaves the barrel however at that point it is still accelerating.
I beg to differ.
It depends on the mass of the object and rate of acceleration.
Think of a bullet being fired from a gun. The bullet is initially at rest until a charge is applied and it then accelerates until equilibrium is achieved before starting to decelerate. Thrust is removed the moment the bullet leaves the barrel however at that point it is still accelerating.
Thrust is removed the moment the bullet leaves the barrel however at that point it is still accelerating.
I'll do your work for you.
Acceleration = force/mass (a reworking of the old F=M/A)
If you have no force then acceleration is zero. If you'd like to explain what positive horizontal force is being applied to a bullet after it has left the barrel, I'll be interested to read it.
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Chimbu
Nope sorry, you are utterly wrong on this. I think maybe you misunderstand the meaning of acceleration - which is defined as a rate of change, not just a change.
As soon as you remove thrust, the speed may appear to increase slightly - but the rate of change is negative (ie a deccelaration). You have alluded to this yourself in the figures you quoted in your post. As acceleration is a vector quantity, as soon as the vector (or rate of change - not just change) starts to reduce, the acceleration becomes negative.
And if you disagree with that, you would need to be able to explain how an object being accelerated can continue to do so when the accelerating force is removed. Inertia doesn't do it; all inertia does is slow the rate of acceleration (or decceleration). Remember, a decrease in the rate of acceleration is actually a decceleration - it is a negative vector.
If you don't believe me, try hanging some fluffy dice from your wet compass. If you accelerate forwards from rest, the fluffy dice will head rearwards - the angle of the string indicating the rate of change. The harder you accelerate, the greater the angle on the string. The proof that the angle of the string is indicating acceleration is that if you stop accelerating and continue moving at a steady speed, the fluffy dice will hang vertically again (ie no angle on the string, therefore no acceleration therefore equilibrium). Going back to our example, if you then remove the power and hit the brakes, the fluffy dice (subject to whatever small inertia they possess) will immediately start to move forwards. The acceleration (as indicated by the angle of the string) immediately reduces (implying negative acceleration or decceleration). The speed will continue to increase for as long as the string is rearwards of vertical, which is never going to be more than a very small fraction of a second.
Any increase you are seeing on the instruments has more to do with lag in in the system than an actual physical increase in speed.
404 Titan
A speed trend arrow is a PREDICTION, not an actual rate change, and isn't reliable in the abort case because the system is simply not set up to measure the extreme velocity change accurately.
ace from space
The same principles apply in a turboprop. Those that don't have a reduced thrust schedule, normally have a thrust augmentation system (ie water meth in the F27 or some J32s).
Besides, a two-engine go-around in the jet is probably just as difficult... ;-)
F.Nose
The mass of the object is what gives it inertia. Acceleration is itself a rate, so to be pedantic you can't have a rate of acceleration (which would be the rate of the rate of change of velocity).
As mentioned above, acceleration is a vector quantity. As soon as the bullet leaves the barrel, the velocity may increase slightly (but only slightly), but the rate of change of velocity (which is what acceleration is) immediately reduces. Think about it - it has to. There is no thrust and lots of drag - the bullet has no choice but to slow down, and more to the point there is no way that the rate of change of velocity can increase when there is no accelerating force...
Looking at it another way, equilibrium is achieved when thrust=drag. This occurs for a very brief instant at the end of the barrel. After that, only deccelaration is happening.
If you have found a way to get the bullet to accelerate when there is no accelerating force, you have basically invented perpetual motion!
No, Remoak.
At the instant that thrust is removed the rate of acceleration starts to decrease but actual deceleration starts some period of time later.
If an aircraft is being accelerated at say 10m/sec/sec it doesn't instantly go to -1m/sec/sec but rather experiences an acceleration rate of 9/8/7/6/5/4/3/2/1 m/sec/sec first.
It may FEEL like deceleration but its actually reducing acceleration.
At the instant that thrust is removed the rate of acceleration starts to decrease but actual deceleration starts some period of time later.
If an aircraft is being accelerated at say 10m/sec/sec it doesn't instantly go to -1m/sec/sec but rather experiences an acceleration rate of 9/8/7/6/5/4/3/2/1 m/sec/sec first.
It may FEEL like deceleration but its actually reducing acceleration.
As soon as you remove thrust, the speed may appear to increase slightly - but the rate of change is negative (ie a deccelaration). You have alluded to this yourself in the figures you quoted in your post. As acceleration is a vector quantity, as soon as the vector (or rate of change - not just change) starts to reduce, the acceleration becomes negative.
And if you disagree with that, you would need to be able to explain how an object being accelerated can continue to do so when the accelerating force is removed. Inertia doesn't do it; all inertia does is slow the rate of acceleration (or decceleration). Remember, a decrease in the rate of acceleration is actually a decceleration - it is a negative vector.
If you don't believe me, try hanging some fluffy dice from your wet compass. If you accelerate forwards from rest, the fluffy dice will head rearwards - the angle of the string indicating the rate of change. The harder you accelerate, the greater the angle on the string. The proof that the angle of the string is indicating acceleration is that if you stop accelerating and continue moving at a steady speed, the fluffy dice will hang vertically again (ie no angle on the string, therefore no acceleration therefore equilibrium). Going back to our example, if you then remove the power and hit the brakes, the fluffy dice (subject to whatever small inertia they possess) will immediately start to move forwards. The acceleration (as indicated by the angle of the string) immediately reduces (implying negative acceleration or decceleration). The speed will continue to increase for as long as the string is rearwards of vertical, which is never going to be more than a very small fraction of a second.
Any increase you are seeing on the instruments has more to do with lag in in the system than an actual physical increase in speed.
404 Titan
I’m not sure what aircraft you fly and/or whether it has a full EFIS setup but the last time I was in the sim the Speed Trend arrow on the speed tape of my PFD didn’t go from acceleration to deceleration in an instant. It did exactly as Chimbu Chuckles has stated. The acceleration decreases over time once the power is reduced or removed before the aircraft started to decelerate.
ace from space
To be fair, comparing an engine failure in a four engine jet with a two engine turbo prop is not comparing apples with apples.
Besides, a two-engine go-around in the jet is probably just as difficult... ;-)
F.Nose
It depends on the mass of the object and rate of acceleration.
Think of a bullet being fired from a gun. The bullet is initially at rest until a charge is applied and it then accelerates until equilibrium is achieved before starting to decelerate. Thrust is removed the moment the bullet leaves the barrel however at that point it is still accelerating.
Think of a bullet being fired from a gun. The bullet is initially at rest until a charge is applied and it then accelerates until equilibrium is achieved before starting to decelerate. Thrust is removed the moment the bullet leaves the barrel however at that point it is still accelerating.
As mentioned above, acceleration is a vector quantity. As soon as the bullet leaves the barrel, the velocity may increase slightly (but only slightly), but the rate of change of velocity (which is what acceleration is) immediately reduces. Think about it - it has to. There is no thrust and lots of drag - the bullet has no choice but to slow down, and more to the point there is no way that the rate of change of velocity can increase when there is no accelerating force...
Looking at it another way, equilibrium is achieved when thrust=drag. This occurs for a very brief instant at the end of the barrel. After that, only deccelaration is happening.
If you have found a way to get the bullet to accelerate when there is no accelerating force, you have basically invented perpetual motion!
the universe is expanding at an increasing rate!!??
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Yes it is, but only because there is a force driving it to do so... but I'm not sure a discussion of dark energy and cosmological constants is appropriate for this forum... 
Moderator
Some interesting posts and worth discussion for the benefit (especially) of the newchums ..
the certification requirements of the aircraft allow for that (2 second recognition time).
only relevant to post A/L 42 certifications. Earlier certifications still are a MOST critical animal when it comes to achieving ASDR.
deceleration starts as soon as you close the thrust levers
afraid you will need to read up a bit in the literature. This is NOT the case, especially for the higher bypass engined aircraft. Throttle chop certainly commands a reduction in thrust. However, as others have pointed out, the engine run down characteristics result in an increase in speed (ie still accelerating) while the thrust sorts itself out, eventually resulting in a deceleration.
If you do exceed V1, it will be by very little.
afraid this is not the case .. Centaurus' figures are not atypical.
I've never seen anyone take two seconds to figure out it was time to stop with a failure, most folk have the thrust levers retarded within half a second.
in the training/checking environment .. of course .. we are all ever so primed for the known-to-be-coming failure that we are ace-of-the-base onto the throttle chop.
On the line, the startle factor historical record proves the need for A/L 42 and, probably, a bit more on many occasions ...
If Vmcg is controlling, you are on the ground, right? That is what Vmcg means.
yes ? and, if this is the situation, you can still end up heading seriously towards the weeds off to the side of the runway in a few blinks of an eye
So in that situation, you control the yaw with asymmetric brake.
basic tenet of certification is that there is no change in thrust or use of braking. If you need to use the brakes .. then you should be stopping rather than trying to recover an already out of control situation
Whatever happened to lowering the nose to, at the worst, maintain level flight while you accelerate?
no real use to the pilot .. in the post departure situation, if you don't reduce thrust .. then it just gets worse .. quickly. Once you reduce thrust, you have some reasonable chance of recovering the situation by accelerating during a descent until you get to a speed at which you can use useful levels of thrust. Mind you .. if you are over the upwind threshold at 100 ft or so ... it probably remains an academic consideration for the Monday morning quarterbackers .. the pilots, generally, being dead shortly thereafter ...
The only time I can see that you would be correct is if you had an unfeathered prop or a similar failure.
that just makes a bad situation worse .. only a matter of degree, not fact.
Of course, if you are talking about GA aircraft at high weights, then sure.
works the same for heavies .. the physics is still the same
With the 146 (and the F27 too I think), under JAA-approved manuals, it was permissible to fly the engine-out departure profile at a speed higher than V2 if that speed had been achieved and the minimum climb gradient was being complied with.
probably never got into the rule book but commonly used as a protocol at operator level .. simply reflects the fact that min V2 is well below the best climb performance speed so, if you are going faster, there is not much point slowing down (caveat - unless a terrain critical escape has turn radii predicated on a scheduled speed)
if you were at training weights, it is actually pretty hard to stop the speed running away a bit while still maintaining a reasonable rate of climb
perhaps you are missing the point of the discussion. If you are fast enough for a yaw departure to be irrelevant, fine .. if you are too slow, you are into a departure and there will be no option to accelerate your way out of a world of hurt .. the thrust just winds you up into a tighter ball in the weeds off to the side of the runway/extended centreline
OK, but I can't think of any transport-category aircraft that wouldn't either accelerate quickly through the danger zone you are describing, or allow a power or pitch reduction to regain control while still climbing away quite happily.
refer to the comments above. The only aircraft which are reasonably bulletproof are those with an ultra low Vmcg/Vmca .. Citation comes to mind.
Main problem is that, unless you have been there or seen it happen, it is difficult to comprehend just how fast the beast can get away from the pilot. I have some interesting Vmcg video footage tucked away somewheres in the archives which opened my eyes .. WIDE .. at the time I first had some involvement with such testing.
The reason I say that it is theoretical, is that you never need to get into that position in the first place.
unless you are in a typical aircraft at min weight using standard min schedule speeds ... and then you are smack bang right in the middle of the problem if you have any hiccups or other problems ..
if you take off using flex thrust there is no requirement to increase thrust to N1ref if you suffer an engine failure.
true, but not particularly relevant to the discussion
I would be interested to know what aircraft you are thinking of when you mention these difficulties.
most of them
Does anyone know the actual method for calculating V1 on the Braz? and Is it possible to get it wrong?
a long time since I have done any work on the -120 so the specifics are a bit rusty. However, speed calculations are conventional .. error potential is no different to other conventional AFMs or RTOW charts developed from the AFM
if there is no thrust there is no acceleration
.. yes ... however, when you chop the operating throttles, there is an engine run down characteristic to take into account .. it DOES take a while for the acceleration to become a deceleration and there WILL be a modest speed increase associated with that sequence
Any increase you are seeing on the instruments has more to do with lag in in the system than an actual physical increase in speed.
afraid this is not the case .. the speed peaks a tad after the throttle chop occurs ... the larger delta occurring for the bigger fan engines
the universe is expanding at an increasing rate!!??
apparently .. but my head hurts when I read those books ..
the certification requirements of the aircraft allow for that (2 second recognition time).
only relevant to post A/L 42 certifications. Earlier certifications still are a MOST critical animal when it comes to achieving ASDR.
deceleration starts as soon as you close the thrust levers
afraid you will need to read up a bit in the literature. This is NOT the case, especially for the higher bypass engined aircraft. Throttle chop certainly commands a reduction in thrust. However, as others have pointed out, the engine run down characteristics result in an increase in speed (ie still accelerating) while the thrust sorts itself out, eventually resulting in a deceleration.
If you do exceed V1, it will be by very little.
afraid this is not the case .. Centaurus' figures are not atypical.
I've never seen anyone take two seconds to figure out it was time to stop with a failure, most folk have the thrust levers retarded within half a second.
in the training/checking environment .. of course .. we are all ever so primed for the known-to-be-coming failure that we are ace-of-the-base onto the throttle chop.
On the line, the startle factor historical record proves the need for A/L 42 and, probably, a bit more on many occasions ...
If Vmcg is controlling, you are on the ground, right? That is what Vmcg means.
yes ? and, if this is the situation, you can still end up heading seriously towards the weeds off to the side of the runway in a few blinks of an eye
So in that situation, you control the yaw with asymmetric brake.
basic tenet of certification is that there is no change in thrust or use of braking. If you need to use the brakes .. then you should be stopping rather than trying to recover an already out of control situation
Whatever happened to lowering the nose to, at the worst, maintain level flight while you accelerate?
no real use to the pilot .. in the post departure situation, if you don't reduce thrust .. then it just gets worse .. quickly. Once you reduce thrust, you have some reasonable chance of recovering the situation by accelerating during a descent until you get to a speed at which you can use useful levels of thrust. Mind you .. if you are over the upwind threshold at 100 ft or so ... it probably remains an academic consideration for the Monday morning quarterbackers .. the pilots, generally, being dead shortly thereafter ...
The only time I can see that you would be correct is if you had an unfeathered prop or a similar failure.
that just makes a bad situation worse .. only a matter of degree, not fact.
Of course, if you are talking about GA aircraft at high weights, then sure.
works the same for heavies .. the physics is still the same
With the 146 (and the F27 too I think), under JAA-approved manuals, it was permissible to fly the engine-out departure profile at a speed higher than V2 if that speed had been achieved and the minimum climb gradient was being complied with.
probably never got into the rule book but commonly used as a protocol at operator level .. simply reflects the fact that min V2 is well below the best climb performance speed so, if you are going faster, there is not much point slowing down (caveat - unless a terrain critical escape has turn radii predicated on a scheduled speed)
if you were at training weights, it is actually pretty hard to stop the speed running away a bit while still maintaining a reasonable rate of climb
perhaps you are missing the point of the discussion. If you are fast enough for a yaw departure to be irrelevant, fine .. if you are too slow, you are into a departure and there will be no option to accelerate your way out of a world of hurt .. the thrust just winds you up into a tighter ball in the weeds off to the side of the runway/extended centreline
OK, but I can't think of any transport-category aircraft that wouldn't either accelerate quickly through the danger zone you are describing, or allow a power or pitch reduction to regain control while still climbing away quite happily.
refer to the comments above. The only aircraft which are reasonably bulletproof are those with an ultra low Vmcg/Vmca .. Citation comes to mind.
Main problem is that, unless you have been there or seen it happen, it is difficult to comprehend just how fast the beast can get away from the pilot. I have some interesting Vmcg video footage tucked away somewheres in the archives which opened my eyes .. WIDE .. at the time I first had some involvement with such testing.
The reason I say that it is theoretical, is that you never need to get into that position in the first place.
unless you are in a typical aircraft at min weight using standard min schedule speeds ... and then you are smack bang right in the middle of the problem if you have any hiccups or other problems ..
if you take off using flex thrust there is no requirement to increase thrust to N1ref if you suffer an engine failure.
true, but not particularly relevant to the discussion
I would be interested to know what aircraft you are thinking of when you mention these difficulties.
most of them
Does anyone know the actual method for calculating V1 on the Braz? and Is it possible to get it wrong?
a long time since I have done any work on the -120 so the specifics are a bit rusty. However, speed calculations are conventional .. error potential is no different to other conventional AFMs or RTOW charts developed from the AFM
if there is no thrust there is no acceleration
.. yes ... however, when you chop the operating throttles, there is an engine run down characteristic to take into account .. it DOES take a while for the acceleration to become a deceleration and there WILL be a modest speed increase associated with that sequence
Any increase you are seeing on the instruments has more to do with lag in in the system than an actual physical increase in speed.
afraid this is not the case .. the speed peaks a tad after the throttle chop occurs ... the larger delta occurring for the bigger fan engines
the universe is expanding at an increasing rate!!??
apparently .. but my head hurts when I read those books ..
That ain't happening at ground idle
Grandpa Aerotart
Nope sorry, you are utterly wrong on this.
I still think that it will take time for drag to overcome the physical acceleration and actually cause deceleration. I agree that the acceleration force is - the instant after thrust is removed but that is not the same as saying the object slows down instantly rather than continuing to pick up a little more speed before physically decelerating. 100 tonnes is going to want to keep doing what it was doing longer than fluffy dice.
Maybe you're correct and all we see is instrument lag - in fact that is ringing a vague bell in a dusty, rarely used section of my grey matter.
Thanks for challenging me to think a bit harder on it.
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afraid you will need to read up a bit in the literature. This is NOT the case, especially for the higher bypass engined aircraft. Throttle chop certainly commands a reduction in thrust. However, as others have pointed out, the engine run down characteristics result in an increase in speed (ie still accelerating) while the thrust sorts itself out, eventually resulting in a deceleration.
afraid this is not the case .. Centaurus' figures are not atypical.
yes ? and, if this is the situation, you can still end up heading seriously towards the weeds off to the side of the runway in a few blinks of an eye
basic tenet of certification is that there is no change in thrust or use of braking. If you need to use the brakes .. then you should be stopping rather than trying to recover an already out of control situation
Once you reduce thrust, you have some reasonable chance of recovering the situation by accelerating during a descent until you get to a speed at which you can use useful levels of thrust.
perhaps you are missing the point of the discussion. If you are fast enough for a yaw departure to be irrelevant, fine .. if you are too slow, you are into a departure and there will be no option to accelerate your way out of a world of hurt .. the thrust just winds you up into a tighter ball in the weeds off to the side of the runway/extended centreline
works the same for heavies .. the physics is still the same
probably never got into the rule book but commonly used as a protocol at operator level
.. yes ... however, when you chop the operating throttles, there is an engine run down characteristic to take into account .. it DOES take a while for the acceleration to become a deceleration and there WILL be a modest speed increase associated with that sequence
Centaurus
True statement except the engines never get to ground idle the instant the throttles hit the stops - they take several seconds to run back - in fact about 10 seconds to reach ground idle from throttle closure from take off power.
I'm happy to be proved wrong, but only if you supply evidence...